This invention relates to the field of direct drive vertical lift and rotation stages for precision motion control. More specifically, it relates to small footprint linear and curvilinear motor driven positioning stages useful in the alignment of optic fibers.
Optic fibers are being used more and more for the transfer of information due to the large bandwidth and insensitivity to certain types of electromagnetic interference. Optic fibers are transparent glass fibers through which light waves encoded with information are passed. The fibers themselves are often less than 100 nm in diameter. Typically, they are enclosed in a protective coating. The fibers are not infinitely long and, therefore, it is necessary to align and bond fibers together. The alignment must be very precise, that is, the centers of the fibers must be aligned in order to minimize power loss across a bonded joint. Not only must the fibers be joined end to end, fibers must be connected to tiny components, such as transmitters, amplifiers and receivers. This process is referred to in the industry as pig-tailing.
In order to position fibers for fiber-to-fiber bonding or pig-tailing automatically, mechanical positioning stages with extremely high resolution and repeatability are required. Very often the bonding and pig-tailing take place in clean rooms. The expense of building and maintaining clean rooms is directly related to the volume of the room. Hence, miniaturization of the mechanical positioning stages for use in optic fiber alignment is extremely critical.
While linear motor driven vertical lift stages have been successfully implemented as disclosed in U.S. Pat. No. 5,731,641, the small footprint requirement for fiber alignment applications and the need to associate a rotation stage over the vertical lift stage has created the need for the advances disclosed herein.
It is an advantage, according to the present invention, to provide a small footprint vertical lift and rotation stage driven by linear and curvilinear motors that have high speed, high accuracy, high repeatability and high position stability making them a superior choice for fiber alignment applications.
Briefly, according to the present invention, there is provided a small footprint vertical lift and rotary positioning stage comprising a base plate, first and second side plates perpendicular to the base plate and fixed near opposite edges of the base plate, a bottom wedge, and a top wedge. The bottom (or drive) wedge has a bottom face parallel with the base plate and an upper face forming an angle alpha with the bottom face. The top (or carriage) wedge has a top face parallel with the base plate and a lower face forming an angle alpha with the top face.
A first linear bearing is positioned between the base plate and the bottom face of the first wedge. A second linear bearing is positioned between the upper face of the bottom wedge and the lower face of the top wedge. Cam grooves are provided in the first plate having cam surfaces for receiving cam follower rollers journaled to the top wedge. The cam surfaces and cam follower rollers constrain the motion of the top wedge in a direction perpendicular to the base. A brushless linear motor comprising an armature winding is fixed to the second side plate. A rare earth magnet track is fixed to the bottom wedge for moving the bottom wedge back and forth along a path constrained by the first linear bearing. As the bottom wedge moves back and forth due to the geometry of the wedges and the cam surfaces and cam rollers, the top wedge is raised and lowered. A linear encoder comprises an encoder reader fixed relative to the base plate and an encoder scale fixed to the bottom wedge extending parallel to the base plate in the direction of travel of the bottom wedge. A rotating stage has a circular plate fixed to the top surface of the top wedge and a circular table rotatably mounted to the circular plate. The table has a first cylindrical flange extending downward from a segment of the circumference of the table outside of one of the side plates. A bracket is mounted on the side of the top wedge extending outwardly of one of the side plates. The bracket supports an upwardly extending second cylindrical flange coaxial with the circular table and the first circular flange. A brushless curvilinear motor comprises an armature winding fixed in the second cylindrical flange and a rare earth magnet track fixed in the first cylindrical flange. An encoder comprising an encoder reader is mounted on the top of the top wedge adjacent the circumference of the table and an encoder scale is mounted on the circumferential edge of the table.